Mailing operations such as bulk mail advertising and delivery of account notices are used by merchants, financial institutions, and others to communicate with existing and prospective customers. Often pre-printed “return” envelopes are included in the mailing for the convenience of customers. Sometimes customer's use commercial checks that are larger than the return envelopes included by the merchants. In such cases, the checks must be folded to fit in the return envelope or the customer must use his own envelope.
An alternative is for the merchant to provide the customer with an adjustable envelope that can be adjusted to a larger size to hold the unfolded check. Several envelopes have been developed that have adjustable sizes. U.S. Pat. No. 1,010,282 issued to Low discloses an envelope that can be adjusted to different sizes to accommodate multiple documents. The envelope body has auxiliary inner and outer closing flaps secured by glue or other means at its ends. The flaps are folded inwardly and superimposed over the envelope body. The outer closing flaps have cutaway portions with arranged tongues extending in the direction of the flap. The tongues are inserted into openings along the length of the flap to keep the envelope closed. U.S. Pat. No. 3,552,640 issued to Young relates to an envelope with pleated side flaps forming folded gussets that unfold to expand the envelope into a box-like configuration. U.S. Pat. No. 3,817,445 issued to Greason discloses an envelope that has two panels joined by an adhesive to form an expandable pocket. The expandable feature is provided by an accordion fold between the longitudinal edges of its two panels. U.S. Pat. No. 5,398,866 issued to Bluemle describes an envelope with pleated side flaps that form a box-like gusset for depth-wise expansion. The side flaps are constructed as side portions of one panel that are foldable longitudinally, with side tongues at the bottom ends. The bottom side tongues serve for closing and adhesively bonding the side flaps to the envelope bottom. The pleated or folded expansion means described in these patents have however been found to be bulky, thus creating difficulties in stacking and bulk packaging of the envelopes. The tongue closure means using are complex, expensive to manufacture, and difficult to use with automated mailing equipment.
What is needed is an adjustable envelope made from a blank that can easily be adjusted from a first size to a second size.